firstly, we don’t know why they are doing this, and we don’t care. You are watching an LED panel, controlled by molten metal. The panel has the leads sticking down below the bottom of the board, so the metal can make connections as it flows past. They are using Wood’s metal, not mercury so it has to be heated to about 159 degrees Fahrenheit to be fluid. This has been representing problems as the metal tends to stick to whatever container he is holding it in. That actually seems to be what most of the writeup and discussion are about, rather than, what it will be used for.